1. Field of the Invention
This invention relates to a cereal separation apparatus for removing inclusions or foreign matters, such as stones, from raw material of cereals such as rice grains, wheat grains and beans, thereby separating the cereals or cereal grains from foreign matters such as stones and straws, and more particularly to a cereal separation apparatus of a type comprising a frame, size grading means mounted at an upper portion of the frame for grading or selecting particles according to the particle size, oscillation- or vibration-type specific gravity grading means mounted at a lower portion of the frame, air flow-producing means for producing an air flow for effecting this specific gravity grading, and a feed passage for feeding the selected or graded raw material from the size grading means to the specific gravity grading means.
Herein, the term "size grading means" is referred to as a structure capable of grading raw material grains (i.e., particle-like matters to be graded) according to the size of the particle-like matters, and this size grading structure may have any mechanical construction as well as any grading principle. The term "size" or "particle size" of the particle-like matter is referred to as a dimension or magnitude in the direction of a minor axis of the particle-like matter.
Herein, the term "specific gravity grading means" is referred to as a structure capable of selecting the raw material grains (i.e., particle-like matters to be graded) according to the specific gravity or density of the particle-like matters, and this specific gravity grading structure can have any mechanical construction as well as any grading principle.
Herein, the term "air flow-producing means" is referred to as a structure capable of producing a flow of the air, and this structure can have any mechanical or electromechanical construction as well as any air flow-producing principle in so far as the structure can cause a pressure difference between its air suction side and its air discharge side so as to produce an air flow therebetween, and as the structure is of such a type that the air will not be substantially contaminated with oil or the like.
2. Related Art
Conventional cereal separation apparatuses of the type mentioned above are described, for example, in U.S. Pat. Nos. 4,971,684, 4,913,804 and 4,652,362.
As shown in FIG. 6, the apparatus 101, disclosed in U.S. Pat. No. 4,971,684, comprises a screening device 102 (serving as a size grading unit) having sorting screens 115 and 118 provided at an upper portion of a frame 108, and a stone sorter 105 (serving as a specific gravity grading unit) which comprises a perforated plate, and is provided at a lower portion of the frame 108. In this apparatus 101, the screening device 102 and the stone sorter 105 are combined together into an integral or unitary oscillation or vibration unit 150 supported on the frame 108 through oscillation or vibration supports 107. The apparatus 101 further comprises an exhaust connection piece 123 (serving as air flow-producing means) for producing an air flow for effecting the specific gravity grading, and a throw-off duct 121 (serving as a feed passage) for feeding the selected raw material from the screening device (size grading unit) 102 to the gravity grading unit. Reference numerals 112 and 113 denote respectively a non-oscillating cover, stationary relative to a floor 109, and a flexible sleeve 113.
In this apparatus 101, the so-called size grading is effected by the screening device 102, and thereafter the so-called specific gravity grading is effected by the stone sorter 105. More specifically, inclusions or foreign matters, such as sand, stone and wood chips, are removed from the raw material grains supplied from a product feed line 110 into the apparatus 101, and are discharged from discharge outlets 116, 120 and 136, and the grains, containing a relatively small amount of such foreign matter, is discharged from an outlet 135. The above U.S. Patent teaches further, in FIG. 3 and others, about circulating the air flow within a range of the stone sorter 105.
However, in the above apparatus 101, the screening device 102 and the stone sorter 105 are arranged in a vertical direction relative to each other, and are formed into the integral oscillation or vibration unit 150, and are vibrated in unison by oscillation or vibration applying mechanism. Therefore, a large load acts on a oscillation or vibration supports 107 of the oscillation unit 150, and therefore the apparatus lacks in durability.
And besides, because of this integral construction, regardless of the nature and conditions of the raw material grains 152 supplied from the product feed line 110 (for example, even when the raw material grains 152 contain a large amount of inclusion foreign matters 153 to be removed by the screening device 102, or even when the raw material grains 152 contain a large amount of inclusion foreign matters 154 to be removed by the stone sorter 105), the optimum vibrations can not be applied respectively to the screening device 102 and the stone sorter 105, and therefore the optimum grading of the raw material grains 152 according to the nature and conditions of the raw material grains 152 could not be effected.
Furthermore, although the screening device 102 can separate from the raw material grains 152 the inclusion foreign matters 153 mixed therein according to their size, this screening device 152 could not satisfactorily remove sand and dust adhering or sticking to the surfaces of the grains 152.
Herein, the term "raw material grains" is referred to as cereals or cereal grains supplied or charged into the cereal separation apparatus so that foreign matters can be separated and removed therefrom by this cereal separation apparatus.
Herein, the term "broken grain" is referred to as a cereal or cereal grain which is at least partially broken into a small particle-like form. The term "normal grains" is referred to as cereals or cereal grains of a normal shape excluding the broken grains. The term "mixture grains" is referred to as a mixture of normal grains and foreign matters other than the normal grains, and is usually referred to as those raw material grains from which foreign matters are partially separated and removed. The term "foreign matter" is usually referred to as those matters except the cereals or cereal grains, such as stone and straw, and in some cases, is also referred to as those grains except the normal grains, as defined for the mixture grains.
Herein, the term "larger", used for foreign matters such as stone, is referred to as that it is larger in size or diameter than the normal grain, and the term "smaller" is referred to as that it is smaller in size or diameter than the normal grain, where the term "size" or "diameter" is defined in connection with whether or not the relevant matter can pass through a hole such as a screen mesh within a normal time period during which the apparatus operates or functions, and usually this term is referred to as a length of a minimum diameter portion or a minor axis. Herein, the term "diameter" is equivalent to the term "size", and does not suggest that the relevant particle-like matter has a circular or oval sectional shape.